Rapamycin promotes endothelial-mesenchymal transition during stress-induced premature senescence through the activation of autophagy

Broadening horizons: molecular mechanisms and disease implications of endothelial-to-mesenchymal transition

Endothelial-mesenchymal transition (EndMT) is defined as an important process of cellular differentiation by which endothelial cells (ECs) are prone to lose their characteristics and transform into mesenchymal cells. During EndMT, reduced expression of endothelial adhesion molecules disrupts intercellular adhesion, triggering cytoskeletal reorganization and mesenchymal transition. Numerous studies have proved that EndMT is a multifaceted biological event driven primarily by cytokines such as TGF-β, TNF-α, and IL-1β, alongside signaling pathways like WNT, Smad, MEK-ERK, and Notch. Nevertheless, the exact roles of EndMT in complicated diseases have not been comprehensively reviewed. In this review, we summarize the predominant molecular regulatory mechanisms and signaling pathways that contribute to the development of EndMT, as well as highlight the contributions of a series of imperative non-coding RNAs in curbing the initiation of EndMT. Furthermore, we discuss the significant impact of EndMT on worsening vasculature-related diseases, including cancer, cardiovascular diseases, atherosclerosis, pulmonary vascular diseases, diabetes-associated fibrotic conditions, and cerebral cavernous malformation, providing the implications that targeting EndMT holds promise as a therapeutic strategy to mitigate disease progression.

Matrix Gla protein suppresses osteoblast senescence and promotes osteogenic differentiation by the PI3K-AKT signaling pathway

Age-related bone loss in mice is associated with senescent cell accumulation and reduced bone formation by osteoblasts. Matrix Gla protein (MGP), secreted by osteoblasts, is pivotal in regulating the bone extracellular matrix mineralization. Previous research has demonstrated that Mgp null mice exhibit osteopenia and fractures, and ultimately die prematurely. To elucidate the mechanisms underlying MGP's role of MGP in bone metabolism, we generated osteoblast-specific Mgp knockout (Mgp cKO) mice by crossing Mgpfl/fl mice with Bglap-Cre mice. The study revealed that in 3-month-old Mgp cKO male mice, trabecular bone volume decreased, and the senescence marker protein p21 increased. Primary osteoblasts from Mgp cKO mice exhibited markers of DNA damage and senescence, such as increased γH2AX foci, p21, and senescence-associated β-galactosidase staining, as well as attenuated cellular proliferation and osteogenic differentiation abilities. In addition, bone marrow stromal cells' colony formation and spontaneous osteogenic ability were impaired in Mgp cKO mice, whereas osteoclastogenesis was enhanced. In vitro treatment with recombinant human MGP promotes osteogenesis in osteoblasts derived from Mgp cKO mice via the PI3K-AKT signaling pathway. Thus, our results suggest that MGP is protective by suppressing osteoblast senescence, offering new insights into potential therapeutic strategies for age-related osteoporosis.

A loss of primary cilia by a reduction in mTOR signaling correlates with age-related deteriorations in condylar cartilage

Age-related deterioration of condylar cartilage is an etiological factor in temporomandibular joint-osteoarthritis (TMJ-OA). However, its underlying mechanism remains unknown. Therefore, we examined age-related changes and the relationship between mTOR signaling and primary cilia in condylar cartilage to determine the intrinsic mechanisms of age-related TMJ-OA. Age-related morphological changes were analyzed using micro-computed tomography and safranin O-stained histological samples of the mandibular condyle of C57BL/6J mice (up to 78 weeks old). Immunohistochemistry was used to assess the activity of mTOR signaling, primary cilia frequency, and Golgi size of condylar chondrocytes. Four-week-old mice receiving an 11-week series of intraperitoneal injections of rapamycin, a potent mTOR signaling inhibitor, were used for the histological evaluation of the condylar cartilage. The condylar cartilage demonstrated an age-related reduction in cartilage area, including chondrocyte size, cell density, and cell size distribution. The Golgi size, primary cilia frequency, and mTOR signaling also decreased with age. Rapamycin injections resulted in both diminished cartilage area and cell size, resembling the phenotypes observed in aged mice. Rapamycin-injected mice also exhibited a smaller Golgi size and lower primary cilia frequency in condylar cartilage. We demonstrated that a loss of primary cilia due to a decline in mTOR signaling was correlated with age-related deteriorations in condylar cartilage. Our findings provide new insights into the tissue homeostasis of condylar cartilage, contributing to understanding the etiology of age-related TMJ-OA.

Decoding senescence of aging single cells at the nexus of biomaterials, microfluidics, and spatial omics

Aging has profound effects on the body, most notably an increase in the prevalence of several diseases. An important aging hallmark is the presence of senescent cells that no longer multiply nor die off properly. Another characteristic is an altered immune system that fails to properly self-surveil. In this multi-player aging process, cellular senescence induces a change in the secretory phenotype, known as senescence-associated secretory phenotype (SASP), of many cells with the intention of recruiting immune cells to accelerate the clearance of these damaged senescent cells. However, the SASP phenotype results in inducing secondary senescence of nearby cells, resulting in those cells becoming senescent, and improper immune activation resulting in a state of chronic inflammation, called inflammaging, in many diseases. Senescence in immune cells, termed immunosenescence, results in further dysregulation of the immune system. An interdisciplinary approach is needed to physiologically assess aging changes of the immune system at the cellular and tissue level. Thus, the intersection of biomaterials, microfluidics, and spatial omics has great potential to collectively model aging and immunosenescence. Each of these approaches mimics unique aspects of the body undergoes as a part of aging. This perspective highlights the key aspects of how biomaterials provide non-cellular cues to cell aging, microfluidics recapitulate flow-induced and multi-cellular dynamics, and spatial omics analyses dissect the coordination of several biomarkers of senescence as a function of cell interactions in distinct tissue environments. An overview of how senescence and immune dysregulation play a role in organ aging, cancer, wound healing, Alzheimer's, and osteoporosis is included. To illuminate the societal impact of aging, an increasing trend in anti-senescence and anti-aging interventions, including pharmacological interventions, medical procedures, and lifestyle changes is discussed, including further context of senescence.

Inhibition of mTOR prevents glucotoxicity-mediated increase of SA-beta-gal, p16INK4a, and insulin hypersecretion, without restoring electrical features of mouse pancreatic islets

An over-activation of the mechanistic target of rapamycin (mTOR) pathway promotes senescence and age-related diseases like type 2 diabetes. Besides, the regenerative potential of pancreatic islets deteriorates with aging. Nevertheless, the role of mTOR on senescence promoted by metabolic stress in islet cells as well as its relevance for electrophysiological aspects is not yet known. Here, we investigated whether parameters suggested to be indicative for senescence are induced in vitro in mouse islet cells by glucotoxicity and if mTOR inhibition plays a protective role against this. Islet cells exhibit a significant increase (~ 76%) in senescence-associated beta-galactosidase (SA-beta-gal) activity after exposure to glucotoxicity for 72 h. Glucotoxicity does not markedly influence p16INK4a protein within 72 h, but p16INK4a levels increase significantly after a 7-days incubation period. mTOR inhibition with a low rapamycin concentration (1 nM) entirely prevents the glucotoxicity-mediated increase of SA-beta-gal and p16INK4a. At the functional level, reactive oxygen species, calcium homeostasis, and electrical activity are disturbed by glucotoxicity, and rapamycin fails to prevent this. In contrast, rapamycin significantly attenuates the insulin hypersecretion promoted by glucotoxicity by modifying the mRNA levels of Vamp2 and Snap25 genes, related to insulin exocytosis. Our data indicate an influence of glucotoxicity on pancreatic islet-cell senescence and a reduction of the senescence markers by mTOR inhibition, which is relevant to preserve the regenerative potential of the islets. Decreasing the influence of mTOR on islet cells exposed to glucotoxicity attenuates insulin hypersecretion, but is not sufficient to prevent electrophysiological disturbances, indicating the involvement of mTOR-independent mechanisms.

Nrf2 Connects Cellular Autophagy and Vascular Senescence in Atherosclerosis: A Mini-Review

Nuclear factor erythroid 2-related factor 2 (Nrf2), a transcriptional factor that maintains intracellular redox equilibrium, modulates the expression of antioxidant genes, scavenger receptors, and cholesterol efflux transporters, all of which contribute significantly to foam cell development and plaque formation. Nrf2 has recently emerged as a key regulator that connects autophagy and vascular senescence in atherosclerosis. Autophagy, a cellular mechanism involved in the breakdown and recycling of damaged proteins and organelles, and cellular senescence, a state of irreversible growth arrest, are both processes implicated in the pathogenesis of atherosclerosis. The intricate interplay of these processes has received increasing attention, shedding light on their cumulative role in driving the development of atherosclerosis. Recent studies have revealed that Nrf2 plays a critical role in mediating autophagy and senescence in atherosclerosis progression. Nrf2 activation promotes autophagy, which increases lipid clearance and prevents the development of foam cells. Meanwhile, the activation of Nrf2 also inhibits cellular senescence by regulating the expression of senescence markers to preserve cellular homeostasis and function and delay the progression of atherosclerosis. This review provides an overview of the molecular mechanisms through which Nrf2 connects cellular autophagy and vascular senescence in atherosclerosis. Understanding these mechanisms can provide insights into potential therapeutic strategies targeting Nrf2 to modulate cellular autophagy and vascular senescence, thereby preventing the progression of atherosclerosis.

Prevention of Chronic Kidney Disease and Its Complications in Older Adults

In an era marked by a global demographic shift towards an aging society, there is a heightened prevalence of chronic kidney disease (CKD) among older adults. The burden of CKD spans from kidney-related complications to impacting psychological well-being, giving rise to depressive symptoms and caregiver burnout. This article delves into CKD prevention strategies within the context of aging, contributing to the discourse by exploring its multifaceted aspects. The prevention of CKD in the older adults necessitates a comprehensive approach. Primary prevention is centered on the modification of risk factors, acknowledging the intricate interplay of various comorbidities. Secondary prevention focuses on early CKD identification. Tertiary prevention aims to address factors contributing to CKD progression and complications, emphasizing the importance of timely interventions. This comprehensive strategy aims to enhance the quality of life for individuals affected by CKD, decelerating the deterioration of functional status. By addressing CKD at multiple levels, this approach seeks to effectively and compassionately care for the aging population.

Risk factors of using late-autophagy inhibitors: Aspects to consider when combined with anticancer therapies

Cancer resistance to therapy is still an unsolved scientific and clinical problem. In 2022, the hallmarks of cancer have been expanded to include four new features, including cellular senescence. Therapy-induced senescence (TIS) is a stressor-based response to conventional treatment methods, e.g. chemo- and radiotherapy, but also to non-conventional targeted therapies. Since TIS reinforces resistance in cancers, new strategies for sensitizing cancer cells to therapy are being adopted. These include macroautophagy as a potential target for inhibition due to its potential cytoprotective role in many cancers. The mechanism of late-stage autophagy inhibitors is based on blockage of autophagolysosome formation or an increase in lysosomal pH, resulting in disrupted cargo degradation. Such inhibitors are relevant candidates for increasing anticancer therapy effectiveness. In particular, 4-aminoquoline derivatives: chloroquine/hydroxychloroquine (CQ/HCQ) have been tested in multiple clinical trials in combination with senescence-inducing anti-cancer drugs. In this review, we summarize the properties of selected late-autophagy inhibitors and their role in the regulation of autophagy and senescent cell phenotype in vitro and in vivo models of cancer as well as treatment response in clinical trials on oncological patients. Additionally, we point out that, although these compounds increase the effectiveness of treatment in some cases, their practical usage might be hindered due to systemic toxicity, hypoxic environment, dose- ant time-dependent inhibitory effects, as well as a possible contribution to escaping from TIS.

Addition of Polyphenols to Drugs: The Potential of Controlling "Inflammaging" and Fibrosis in Human Senescent Lung Fibroblasts In Vitro

The combination of a polyphenol, quercetin, with dasatinib initiated clinical trials to evaluate the safety and efficacy of senolytics in idiopathic pulmonary fibrosis, a lung disease associated with the presence of senescent cells. Another approach to senotherapeutics consists of controlling inflammation related to cellular senescence or "inflammaging", which participates, among other processes, in establishing pulmonary fibrosis. We evaluate whether polyphenols such as caffeic acid, chlorogenic acid, epicatechin, gallic acid, quercetin, or resveratrol combined with different senotherapeutics such as metformin or rapamycin, and antifibrotic drugs such as nintedanib or pirfenidone, could present beneficial actions in an in vitro model of senescent MRC-5 lung fibroblasts. A senescent-associated secretory phenotype (SASP) was evaluated by the measurement of interleukin (IL)-6, IL-8, and IL-1β. The senescent-associated β-galactosidase (SA-β-gal) activity and cellular proliferation were assessed. Fibrosis was evaluated using a Picrosirius red assay and the gene expression of fibrosis-related genes. Epithelial-mesenchymal transition (EMT) was assayed in the A549 cell line exposed to Transforming Growth Factor (TGF)-β in vitro. The combination that demonstrated the best results was metformin and caffeic acid, by inhibiting IL-6 and IL-8 in senescent MRC-5 cells. Metformin and caffeic acid also restore cellular proliferation and reduce SA-β-gal activity during senescence induction. The collagen production by senescent MRC-5 cells was inhibited by epicatechin alone or combined with drugs. Epicatechin and nintedanib were able to control EMT in A549 cells. In conclusion, caffeic acid and epicatechin can potentially increase the effectiveness of senotherapeutic drugs in controlling lung diseases whose pathophysiological component is the presence of senescent cells and fibrosis.

Elucidating the crosstalk between endothelial-to-mesenchymal transition (EndoMT) and endothelial autophagy in the pathogenesis of atherosclerosis

Atherosclerosis, a chronic systemic inflammatory condition, is implicated in most cardiovascular ischemic events. The pathophysiology of atherosclerosis involves various cell types and associated processes, including endothelial cell activation, monocyte recruitment, smooth muscle cell migration, involvement of macrophages and foam cells, and instability of the extracellular matrix. The process of endothelial-to-mesenchymal transition (EndoMT) has recently emerged as a pivotal process in mediating vascular inflammation associated with atherosclerosis. This transition occurs gradually, with a significant portion of endothelial cells adopting an intermediate state, characterized by a partial loss of endothelial-specific gene expression and the acquisition of "mesenchymal" traits. Consequently, this shift disrupts endothelial cell junctions, increases vascular permeability, and exacerbates inflammation, creating a self-perpetuating cycle that drives atherosclerotic progression. While endothelial cell dysfunction initiates the development of atherosclerosis, autophagy, a cellular catabolic process designed to safeguard cells by recycling intracellular molecules, is believed to exert a significant role in plaque development. Identifying the pathological mechanisms and molecular mediators of EndoMT underpinning endothelial autophagy, may be of clinical relevance. Here, we offer new insights into the underlying biology of atherosclerosis and present potential molecular mechanisms of atherosclerotic resistance and highlight potential therapeutic targets.

Cellular senescence in acute kidney injury: Target and opportunity

Acute kidney injury (AKI) is a common clinical disease with a high incidence and mortality rate. It typically arises from hemodynamic alterations, sepsis, contrast agents, and toxic drugs, instigating a series of events that culminate in tissue and renal damage. This sequence of processes often leads to acute renal impairment, prompting the initiation of a repair response. Cellular senescence is an irreversible arrest of the cell cycle. Studies have shown that renal cellular senescence is closely associated with AKI through several mechanisms, including the promotion of oxidative stress and inflammatory response, telomere shortening, and the down-regulation of klotho expression. Exploring the role of cellular senescence in AKI provides innovative therapeutic ideas for both the prevention and treatment of AKI. Furthermore, it has been observed that targeted removal of senescent cells in vivo can efficiently postpone senescence, resulting in an enhanced prognosis for diseases associated with senescence. This article explores the effects of common anti-senescence drugs senolytics and senostatic and lifestyle interventions on renal diseases, and mentions the rapid development of mesenchymal stem cells (MSCs). These studies have taken senescence-related research to a new level. Overall, this article comprehensively summarizes the studies on cellular senescence in AKI, aiming is to elucidate the relationship between cellular senescence and AKI, and explore treatment strategies to improve the prognosis of AKI.

Endothelial cell-specific reduction in mTOR ameliorates age-related arterial and metabolic dysfunction

Systemic inhibition of the mammalian target of rapamycin (mTOR) delays aging and many age-related conditions including arterial and metabolic dysfunction. However, the mechanisms and tissues involved in these beneficial effects remain largely unknown. Here, we demonstrate that activation of S6K, a downstream target of mTOR, is increased in arteries with advancing age, and that this occurs preferentially in the endothelium compared with the vascular smooth muscle. Induced endothelial cell-specific deletion of mTOR reduced protein expression by 60-70%. Although this did not significantly alter arterial and metabolic function in young mice, endothelial mTOR reduction reversed arterial stiffening and improved endothelium-dependent dilation (EDD) in old mice, indicating an improvement in age-related arterial dysfunction. Improvement in arterial function in old mice was concomitant with reductions in arterial cellular senescence, inflammation, and oxidative stress. The reduction in endothelial mTOR also improved glucose tolerance in old mice, and this was associated with attenuated hepatic gluconeogenesis and improved lipid tolerance, but was independent of alterations in peripheral insulin sensitivity, pancreatic beta cell function, or fasted plasma lipids in old mice. Lastly, we found that endothelial mTOR reduction suppressed gene expression of senescence and inflammatory markers in endothelial-rich (i.e., lung) and metabolically active organs (i.e., liver and adipose tissue), which may have contributed to the improvement in metabolic function in old mice. This is the first evidence demonstrating that reducing endothelial mTOR in old age improves arterial and metabolic function. These findings have implications for future drug development.

Rapamycin protects mouse skin from ultraviolet B-induced photodamage by modulating Hspb2-mediated autophagy and apoptosis

BACKGROUND

Continuous exposure to UVB is the main extrinsic cause of skin photodamage, which is associated with oxidative stress, DNA damage, apoptosis and degradation of collagen. Rapamycin, a mechanistic target inhibitor of rapamycin complex 1 (mTORC1), has been shown to play a crucial role anti-tumor and aging retardation, but its mechanism of action in UVB-induced photodamage still remains unknown. In this study, we investigated the role of rapamycin and Hspb2 (also known as Hsp27) in UVB-induced photodamage in mice.

METHODS AND RESULTS

We constructed skin acute photodamage models on the ears of WT and Hspb2 KO mice, respectively, and administered rapamycin treatment. Histological results showed that knockout of the hspb2 exacerbated the skin damage, as evidenced by thickening of the epidermis, breakage and disruption of collagen fibers and reduction in their number, which is reversed by rapamycin treatment. In addition, hspb2 knockout promoted UVB-induced apoptosis and reduced autophagy levels, with a significant increase in p53 levels and Bax/Bcl-2 ratio, a reduction in LC3II/I ratio and an increase in p62 levels in the KO mice compared to those in WT mice after the same dose of UVB irradiation. Rapamycin was also found to inhibit collagen degradation induced by hspb2 knockdown through activation of the TGF-β/Smad signaling pathway.

CONCLUSIONS

Rapamycin can alleviate skin photodamage from Hspb2 knockout to some extent. It may be a potential therapeutic drug for skin photodamage. In this study, we investigated the role of rapamycin and Hspb2 in UVB-induced photodamage in mice. Histological results showed that knockout of the hspb2 exacerbated the skin damage, as evidenced by thickening of the epidermis, breakage and disruption of collagen fibers and reduction in their number, which is reversed by rapamycin treatment. In addition, hspb2 knockout promoted UVB-induced apoptosis and reduced autophagy levels. Rapamycin was also found to inhibit collagen degradation induced by hspb2 knockdown through activation of the TGF-β/Smad signaling pathway. We conclude that rapamycin and Hspb2 exert a synergistic protective effect in skin photodamage.

Translating Senotherapeutic Interventions into the Clinic with Emerging Proteomic Technologies

Cellular senescence is a state of irreversible growth arrest with profound phenotypic changes, including the senescence-associated secretory phenotype (SASP). Senescent cell accumulation contributes to aging and many pathologies including chronic inflammation, type 2 diabetes, cancer, and neurodegeneration. Targeted removal of senescent cells in preclinical models promotes health and longevity, suggesting that the selective elimination of senescent cells is a promising therapeutic approach for mitigating a myriad of age-related pathologies in humans. However, moving senescence-targeting drugs (senotherapeutics) into the clinic will require therapeutic targets and biomarkers, fueled by an improved understanding of the complex and dynamic biology of senescent cell populations and their molecular profiles, as well as the mechanisms underlying the emergence and maintenance of senescence cells and the SASP. Advances in mass spectrometry-based proteomic technologies and workflows have the potential to address these needs. Here, we review the state of translational senescence research and how proteomic approaches have added to our knowledge of senescence biology to date. Further, we lay out a roadmap from fundamental biological discovery to the clinical translation of senotherapeutic approaches through the development and application of emerging proteomic technologies, including targeted and untargeted proteomic approaches, bottom-up and top-down methods, stability proteomics, and surfaceomics. These technologies are integral for probing the cellular composition and dynamics of senescent cells and, ultimately, the development of senotype-specific biomarkers and senotherapeutics (senolytics and senomorphics). This review aims to highlight emerging areas and applications of proteomics that will aid in exploring new senescent cell biology and the future translation of senotherapeutics.

Endothelial to Mesenchymal Transition in Health and Disease

The endothelium is one of the largest organ systems in the body, and data continue to emerge regarding the importance of endothelial cell (EC) dysfunction in vascular aging and a range of cardiovascular diseases (CVDs). Over the last two decades and as a process intimately related to EC dysfunction, an increasing number of studies have also implicated endothelial to mesenchymal transition (EndMT) as a potentially disease-causal pathobiologic process that is involved in a multitude of differing CVDs. However, EndMT is also involved in physiologic processes (e.g., cardiac development), and transient EndMT may contribute to vascular regeneration in certain contexts. Given that EndMT involves a major alteration in the EC-specific molecular program, and that it potentially contributes to CVD pathobiology, the clinical translation opportunities are significant, but further molecular and translational research is needed to see these opportunities realized.

The Potential of Senescence as a Target for Developing Anticancer Therapy

Senescence occurs in response to various stimuli. Senescence has attracted attention because of its potential use in anticancer therapy as it plays a tumor-suppressive role. It also promotes tumorigeneses and therapeutic resistance. Since senescence can induce therapeutic resistance, targeting senescence may help to overcome therapeutic resistance. This review provides the mechanisms of senescence induction and the roles of the senescence-associated secretory phenotype (SASP) in various life processes, including therapeutic resistance and tumorigenesis. The SASP exerts pro-tumorigenic or antitumorigenic effects in a context-dependent manner. This review also discusses the roles of autophagy, histone deacetylases (HDACs), and microRNAs in senescence. Many reports have suggested that targeting HDACs or miRNAs could induce senescence, which, in turn, could enhance the effects of current anticancer drugs. This review presents the view that senescence induction is a powerful method of inhibiting cancer cell proliferation.

Cellular senescence: the good, the bad and the unknown

Cellular senescence is a ubiquitous process with roles in tissue remodelling, including wound repair and embryogenesis. However, prolonged senescence can be maladaptive, leading to cancer development and age-related diseases. Cellular senescence involves cell-cycle arrest and the release of inflammatory cytokines with autocrine, paracrine and endocrine activities. Senescent cells also exhibit morphological alterations, including flattened cell bodies, vacuolization and granularity in the cytoplasm and abnormal organelles. Several biomarkers of cellular senescence have been identified, including SA-βgal, p16 and p21; however, few markers have high sensitivity and specificity. In addition to driving ageing, senescence of immune and parenchymal cells contributes to the development of a variety of diseases and metabolic disorders. In the kidney, senescence might have beneficial roles during development and recovery from injury, but can also contribute to the progression of acute kidney injury and chronic kidney disease. Therapies that target senescence, including senolytic and senomorphic drugs, stem cell therapies and other interventions, have been shown to extend lifespan and reduce tissue injury in various animal models. Early clinical trials confirm that senotherapeutic approaches could be beneficial in human disease. However, larger clinical trials are needed to translate these approaches to patient care.

Endothelial Autophagy in Coronary Microvascular Dysfunction and Cardiovascular Disease

Coronary microvascular dysfunction (CMD) refers to a subset of structural and/or functional disorders of coronary microcirculation that lead to impaired coronary blood flow and eventually myocardial ischemia. Amid the growing knowledge of the pathophysiological mechanisms and the development of advanced tools for assessment, CMD has emerged as a prevalent cause of a broad spectrum of cardiovascular diseases (CVDs), including obstructive and nonobstructive coronary artery disease, diabetic cardiomyopathy, and heart failure with preserved ejection fraction. Of note, the endothelium exerts vital functions in regulating coronary microvascular and cardiac function. Importantly, insufficient or uncontrolled activation of endothelial autophagy facilitates the pathogenesis of CMD in diverse CVDs. Here, we review the progress in understanding the pathophysiological mechanisms of autophagy in coronary endothelial cells and discuss their potential role in CMD and CVDs.

Senescence: Pathogenic Driver in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is recognized as a disease of accelerated lung aging. Over the past two decades, mounting evidence suggests an accumulation of senescent cells within the lungs of patients with COPD that contributes to dysregulated tissue repair and the secretion of multiple inflammatory proteins, termed the senescence-associated secretory phenotype (SASP). Cellular senescence in COPD is linked to telomere dysfunction, DNA damage, and oxidative stress. This review gives an overview of the mechanistic contributions and pathologic consequences of cellular senescence in COPD and discusses potential therapeutic approaches targeting senescence-associated signaling in COPD.

Extravascular rapamycin film inhibits the endothelial-to-mesenchymal transition through the autophagy pathway to prevent vein graft restenosis

Following vein grafting, the vein must adapt to arterial hemodynamics, which can lead to intimal hyperplasia (IH) and restenosis. Moreover, endothelial-to-mesenchymal transition (EndMT) components are highly associated with IH. Therefore, in this study, we aimed to design an extravascular film loaded with rapamycin (extravascular rapamycin film [ERF]) to limit vein graft stenosis. The film exhibited stable physicochemical properties as well as in vivo and in vitro biocompatibility. In vivo, the film inhibited the EndMT by activating the autophagy pathway. Moreover, rapamycin enhanced this biological effect. Collectively, these findings highlighted the applicability of ERF as a new therapeutic target for preventing vein graft restenosis.

Deep models of integrated multiscale molecular data decipher the endothelial cell response to ionizing radiation

The vascular endothelium is a hot spot in the response to radiation therapy for both tumors and normal tissues. To improve patient outcomes, interpretable systemic hypotheses are needed to help radiobiologists and radiation oncologists propose endothelial targets that could protect normal tissues from the adverse effects of radiation therapy and/or enhance its antitumor potential. To this end, we captured the kinetics of multi-omics layers-i.e. miRNome, targeted transcriptome, proteome, and metabolome-in irradiated primary human endothelial cells cultured in vitro. We then designed a strategy of deep learning as in convolutional graph networks that facilitates unsupervised high-level feature extraction of important omics data to learn how ionizing radiation-induced endothelial dysfunction may evolve over time. Last, we present experimental data showing that some of the features identified using our approach are involved in the alteration of angiogenesis by ionizing radiation.

Sorafenib, rapamycin, and venetoclax attenuate doxorubicin-induced senescence and promote apoptosis in HCT116 cells

Emerging evidence has shown that the therapy-induced senescent growth arrest in cancer cells is of durable nature whereby a subset of cells can reinstate proliferative capacity. Promising new drugs named senolytics selectively target senescent cells and commit them into apoptosis. Accordingly, senolytics have been proposed as adjuvant cancer treatment to cull senescent tumor cells, and thus, screening for agents that exhibit senolytic properties is highly warranted. Our study aimed to investigate three agents, sorafenib, rapamycin, and venetoclax for their senolytic potential in doxorubicin-induced senescence in HCT116 cells. HCT116 cells were treated with one of the three agents, sorafenib (5 µM), rapamycin (100 nM), or venetoclax (10 µM), in the absence or presence of doxorubicin (1 µM). Senescence was evaluated using microscopy-based and flow cytometry-based Senescence-associated-β-galactosidase staining (SA-β-gal), while apoptosis was assessed using annexin V-FITC/PI, and Muse caspase-3/-7 activity assays. We screened for potential genes through which the three drugs exerted senolytic-like action using the Human Cancer Pathway Finder PCR array. The three agents reduced doxorubicin-induced senescent cell subpopulations and significantly enhanced the apoptotic effect of doxorubicin compared with those treated only with doxorubicin. The senescence genes IGFBP5 and BMI1 and the apoptosis genes CASP7 and CASP9 emerged as candidate genes through which the three drugs exhibited senolytic-like properties. These results suggest that the attenuation of doxorubicin-induced senescence might have shifted HCT116 cells to apoptosis by exposure to the tested pharmacological agents. Our work argues for the use of senolytics to reduce senescence-mediated resistance in tumor cells and to enhance chemotherapy efficacy.

Dissecting primary and secondary senescence to enable new senotherapeutic strategies

Cellular senescence is a state of stable cell cycle arrest that is known to be elicited in response to different stresses or forms of damage. Senescence limits the replication of old, damaged, and precancerous cells in the short-term but is implicated in diseases and debilities of aging due to loss of regenerative reserve and secretion of a complex combination of factors called the senescence-associated secretory phenotype (SASP). More recently, investigators have discovered that senescent cells induced by these methods (what we term "primary senescent cells") are also capable of inducing other non-senescent cells to undergo senescence - a phenomenon we call "secondary senescence." Secondary senescence has been demonstrated to occur via two broad types of mechanisms. First, factors in the SASP have been shown to be involved in spreading senescence; we call this phenomenon "paracrine senescence." Second, primary senescent cells can induce senescence via an additional group of mechanisms involving cell-to-cell contacts of different types; we term this phenomenon "juxtacrine senescence." "Secondary senescence" in our definition is thus the overarching term for both paracrine and juxtacrine senescence together. By allowing cells that are inherently small in number and incapable of replication to increase in number and possibly spread to anatomically distant locations, secondary senescence allows an initially small number of senescent cells to contribute further to age-related pathologies. We propose that understanding how primary and secondary senescent cells differ from each other and the mechanisms of their spread will enable the development of new rejuvenation therapies to target different senescent cell populations and interrupt their spread, extending human health- and potentially lifespan.

New Insights into Profibrotic Myofibroblast Formation in Systemic Sclerosis: When the Vascular Wall Becomes the Enemy

In systemic sclerosis (SSc), abnormalities in microvessel morphology occur early and evolve into a distinctive vasculopathy that relentlessly advances in parallel with the development of tissue fibrosis orchestrated by myofibroblasts in nearly all affected organs. Our knowledge of the cellular and molecular mechanisms underlying such a unique relationship between SSc-related vasculopathy and fibrosis has profoundly changed over the last few years. Indeed, increasing evidence has suggested that endothelial-to-mesenchymal transition (EndoMT), a process in which profibrotic myofibroblasts originate from endothelial cells, may take center stage in SSc pathogenesis. While in arterioles and small arteries EndoMT may lead to the accumulation of myofibroblasts within the vessel wall and development of fibroproliferative vascular lesions, in capillary vessels it may instead result in vascular destruction and formation of myofibroblasts that migrate into the perivascular space with consequent tissue fibrosis and microvessel rarefaction, which are hallmarks of SSc. Besides endothelial cells, other vascular wall-resident cells, such as pericytes and vascular smooth muscle cells, may acquire a myofibroblast-like synthetic phenotype contributing to both SSc-related vascular dysfunction and fibrosis. A deeper understanding of the mechanisms underlying the differentiation of myofibroblasts inside the vessel wall provides the rationale for novel targeted therapeutic strategies for the treatment of SSc.

Endothelial Dysfunction in Atherosclerotic Cardiovascular Diseases and Beyond: From Mechanism to Pharmacotherapies

The endothelium, a cellular monolayer lining the blood vessel wall, plays a critical role in maintaining multiorgan health and homeostasis. Endothelial functions in health include dynamic maintenance of vascular tone, angiogenesis, hemostasis, and the provision of an antioxidant, anti-inflammatory, and antithrombotic interface. Dysfunction of the vascular endothelium presents with impaired endothelium-dependent vasodilation, heightened oxidative stress, chronic inflammation, leukocyte adhesion and hyperpermeability, and endothelial cell senescence. Recent studies have implicated altered endothelial cell metabolism and endothelial-to-mesenchymal transition as new features of endothelial dysfunction. Endothelial dysfunction is regarded as a hallmark of many diverse human panvascular diseases, including atherosclerosis, hypertension, and diabetes. Endothelial dysfunction has also been implicated in severe coronavirus disease 2019. Many clinically used pharmacotherapies, ranging from traditional lipid-lowering drugs, antihypertensive drugs, and antidiabetic drugs to proprotein convertase subtilisin/kexin type 9 inhibitors and interleukin 1β monoclonal antibodies, counter endothelial dysfunction as part of their clinical benefits. The regulation of endothelial dysfunction by noncoding RNAs has provided novel insights into these newly described regulators of endothelial dysfunction, thus yielding potential new therapeutic approaches. Altogether, a better understanding of the versatile (dys)functions of endothelial cells will not only deepen our comprehension of human diseases but also accelerate effective therapeutic drug discovery. In this review, we provide a timely overview of the multiple layers of endothelial function, describe the consequences and mechanisms of endothelial dysfunction, and identify pathways to effective targeted therapies. SIGNIFICANCE STATEMENT: The endothelium was initially considered to be a semipermeable biomechanical barrier and gatekeeper of vascular health. In recent decades, a deepened understanding of the biological functions of the endothelium has led to its recognition as a ubiquitous tissue regulating vascular tone, cell behavior, innate immunity, cell-cell interactions, and cell metabolism in the vessel wall. Endothelial dysfunction is the hallmark of cardiovascular, metabolic, and emerging infectious diseases. Pharmacotherapies targeting endothelial dysfunction have potential for treatment of cardiovascular and many other diseases.

Vascular Endothelial Senescence: Pathobiological Insights, Emerging Long Noncoding RNA Targets, Challenges and Therapeutic Opportunities

Cellular senescence is a stable form of cell cycle arrest in response to various stressors. While it serves as an endogenous pro-resolving mechanism, detrimental effects ensue when it is dysregulated. In this review, we introduce recent advances for cellular senescence and inflammaging, the underlying mechanisms for the reduction of nicotinamide adenine dinucleotide in tissues during aging, new knowledge learned from p16 reporter mice, and the development of machine learning algorithms in cellular senescence. We focus on pathobiological insights underlying cellular senescence of the vascular endothelium, a critical interface between blood and all tissues. Common causes and hallmarks of endothelial senescence are highlighted as well as recent advances in endothelial senescence. The regulation of cellular senescence involves multiple mechanistic layers involving chromatin, DNA, RNA, and protein levels. New targets are discussed including the roles of long noncoding RNAs in regulating endothelial cellular senescence. Emerging small molecules are highlighted that have anti-aging or anti-senescence effects in age-related diseases and impact homeostatic control of the vascular endothelium. Lastly, challenges and future directions are discussed including heterogeneity of endothelial cells and endothelial senescence, senescent markers and detection of senescent endothelial cells, evolutionary differences for immune surveillance in mice and humans, and long noncoding RNAs as therapeutic targets in attenuating cellular senescence. Accumulating studies indicate that cellular senescence is reversible. A better understanding of endothelial cellular senescence through lifestyle and pharmacological interventions holds promise to foster a new frontier in the management of cardiovascular disease risk.

Endothelial-to-mesenchymal transition in systemic sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by significant vascular alterations and multi-organ fibrosis. Microvascular alterations are the first event of SSc and injured endothelial cells (ECs) may transdifferentiate towards myofibroblasts, the cells responsible for fibrosis and collagen deposition. This process is identified as endothelial-to-mesenchymal transition (EndMT), and understanding of its development is pivotal to identify early pathogenetic events and new therapeutic targets for SSc. In this review, we have highlighted the molecular mechanisms of EndMT and summarize the evidence of the role played by EndMT during the development of progressive fibrosis in SSc, also exploring the possible therapeutic role of its inhibition.

Impaired ATG16L-Dependent Autophagy Promotes Renal Interstitial Fibrosis in Chronic Renal Graft Dysfunction Through Inducing EndMT by NF-κB Signal Pathway

Chronic renal graft dysfunction (CAD) is caused by multiple factors, including glomerular sclerosis, inflammation, interstitial fibrosis and tubular atrophy (IF/TA). However, the most prominent elements of CAD are IF/TA. Our studies have confirmed that endothelial-mesenchymal transition (EndMT) is an important source to allograft IF/TA. The characteristic of EndMT is the loss of endothelial marker and the acquisition of mesenchymal or fibroblastic phenotypes. Autophagy is an intracellular degradation pathway that is regulated by autophagy-related proteins and plays a vital role in many fibrotic conditions. However, whether or not autophagy contributes to fibrosis of renal allograft and how such mechanism occurs still remains unclear. Autophagy related 16 like gene (ATG16L) is a critical autophagy-related gene (ARG) necessary for autophagosome formation. Here, we first analyzed kidney transplant patient tissues from Gene Expression Omnibus (GEO) datasets and 60 transplant patients from our center. Recipients with stable kidney function were defined as non-CAD group and all patients in CAD group were histopathologically diagnosed with CAD. Results showed that ATG16L, as one significant differential ARG, was less expressed in CAD group compared to the non-CAD group. Furthermore, we found there were less autophagosomes and autolysosomes in transplanted kidneys of CAD patients, and downregulation of autophagy is a poor prognostic factor. In vitro, we found out that the knockdown of ATG16L enhanced the process of EndMT in human renal glomerular endothelial cells (HRGECs). In vivo, the changes of EndMT and autophagic flux were then detected in rat renal transplant models of CAD. We demonstrated the occurrence of EndMT, and indicated that abundance of ATG16L was accompanied by the dynamic autophagic flux change along different stages of kidney transplantation. Mechanistically, knockdown of ATG16L, specifically in endothelial cells, reduced of NF-κB degradation and excreted inflammatory cytokines (IL-1β, IL-6 and TNF-α), which could facilitate EndMT. In conclusion, ATG16L-dependent autophagic flux causing by transplant showed progressive loss increase over time. Inflammatory cytokines from this process promoted EndMT, thereby leading to progression of CAD. ATG16L served as a negative regulator of EndMT and development of renal graft fibrosis, and autophagy can be explored as a potential therapeutic target for chronic renal graft dysfunction.

Cellular Senescence Affects Cardiac Regeneration and Repair in Ischemic Heart Disease

Ischemic heart disease (IHD) is defined as a syndrome of ischemic cardiomyopathy. Myogenesis and angiogenesis in the ischemic myocardium are important for cardiomyocyte (CM) survival, improving cardiac function and decreasing the progression of heart failure after IHD. Cellular senescence is a state of permanent irreversible cell cycle arrest caused by stress that results in a decline in cellular functions, such as proliferation, migration, homing, and differentiation. In addition, senescent cells produce the senescence-associated secretory phenotype (SASP), which affects the tissue microenvironment and surrounding cells by secreting proinflammatory cytokines, chemokines, growth factors, and extracellular matrix degradation proteins. The accumulation of cardiovascular-related senescent cells, including vascular endothelial cells (VECs), vascular smooth muscle cells (VSMCs), CMs and progenitor cells, is an important risk factor of cardiovascular diseases, such as vascular aging, atherosclerotic plaque formation, myocardial infarction (MI) and ventricular remodeling. This review summarizes the processes of angiogenesis, myogenesis and cellular senescence after IHD. In addition, this review focuses on the relationship between cellular senescence and cardiovascular disease and the mechanism of cellular senescence. Finally, we discuss a potential therapeutic strategy for MI targeting senescent cells.

Muscovy duck reovirus promotes virus replication by inhibiting autophagy-lysosomal degradation pathway

Autophagy plays a momentous role in cellular responses against pathogens. However, the influence of the autophagy machinery on Muscovy duck reovirus (MDRV) infection is not yet confirmed. In this study, it was shown that MDRV infection significantly increased the number of autophagy-like vesicles in DF-1 cells under electron microscope and the LC3-I/LC3-II conversion, which was considered important indicators of autophagy. It was worth noting that the level of autophagy was positively correlated with MDRV replication. Further test results showed that MDRV-induced autophagy can promote virus replication in DF-1 cells, and both the envelope protein sigma A and non-structural protein sigma NS that play an important role in virus replication process can colocalize with the autophagosome marker molecule LC3-II by confocal immunofluorescence analysis. These results indicated that MDRV utilized the autophagosomes for replication. Through transfection of the dual fluorescent plasmid mcherry-EGFP-LC3 and fluorescence microscope observation, it was found that autophagosomes were more likely to fuse with lysosomes in MDRV-infected cells compared with the blank group. The phenomenon of pEGFP-LC3B fluorescent spot and LAMP1 co-localization appeared in MDRV infected cells, indicating that MDRV infection would promote the fusion of autophagosomes and the lysosomes. Conversely, accumulation of p62 was observed by immunoblotting, suggesting that autolysosomes does not exert effective degradation. MDRV infection triggered a incomplete autophagic response. Further studies found that the expression of LAMP1, a marker protein of late endosome/early lysosome, increased significantly in MDRV-infected cells, suggesting an increase in the number of immature lysosomes. In addition, the experiment detected the maturation of the lysosomal acid hydrolase Cathepsin D in the cells, and found that the expression of the 33 kDa mature form of Cathepsin D was significantly reduced after MDRV infection, indicating that MDRV inhibits the maturation of lysosomes. In general, MDRV infection induces autophagy of DF-1 cells, promotes the fusion of autophagosomes and lysosomes, inhibits autophagolysosome degradation, and promotes virus replication.

Combination Strategies to Improve Targeted Radionuclide Therapy

In recent years, targeted radionuclide therapy (TRT) has emerged as a promising strategy for cancer treatment. In contrast to conventional radiotherapy, TRT delivers ionizing radiation to tumors in a targeted manner, reducing the dose that healthy tissues are exposed to. Existing TRT strategies include the use of 177Lu-DOTATATE, 131I-metaiodobenzylguanidine, Bexxar, and Zevalin, clinically approved agents for the treatment of neuroendocrine tumors, neuroblastoma, and non-Hodgkin lymphoma, respectively. Although promising results have been obtained with these agents, clinical evidence acquired to date suggests that only a small percentage of patients achieves complete response. Consequently, there have been attempts to improve TRT outcomes through combinations with other therapeutic agents; such strategies include administering concurrent TRT and chemotherapy, and the use of TRT with known or putative radiosensitizers such as poly(adenosine diphosphate ribose) polymerase and mammalian-target-of-rapamycin inhibitors. In addition to potentially achieving greater therapeutic effects than the respective monotherapies, these strategies may lead to lower dosages or numbers of cycles required and, in turn, reduce unwanted toxicities. As of now, several clinical trials have been conducted to assess the benefits of TRT-based combination therapies, sometimes despite limited preclinical evidence being available in the public domain to support their use. Although some clinical trials have yielded promising results, others have shown no clear survival benefit from particular combination treatments. Here, we present a comprehensive review of combination strategies with TRT reported in the literature to date and evaluate their therapeutic potential.